M57 - The Ring Nebula

The Ring Nebula in Lyra is another old favourite of astroimagers. The above image (click on the image to emlarge) was taken in September 2007 with the SXV-H9 camera and the Vixen VMC200L (200mm/f9) and was assembled from 20 X 60 second exposures in white light as a luminance frame, with 30 X 60 exposures through a Ha (red channel) filter, with a further 30 X 60 exposures through an O3 (blue channel) filter, all in 2x2 binned mode. The raw frames for each channel were stacked and contrast-adjusted in AIP4Win, then exported as TIFs to Paint Shop Pro, where I used the colour masking technique in "Layers" as described earlier to assemble the final colour image as above.

I had a little difficulty focussing and wasn't too happy with the final star images. After the imaging session, I replaced the CCD with an eyepiece and found that the 'scope was actually rather out of collimation. This was the first time in five years that I had needed to tweak the collimation on the VC200L - it has a double set of push-pull screws to adjust both primary and secondary mirrors, which tend to lock the mirrors in place and keep collimation pretty well. However, I remembered that I had hastily abandoned my last imaging session when a sudden rainstorm had hit, and that I had to remove my rig from its platform and wheel it to shelter pretty quickly when the first big drops of rain started to fall. I guess the hurried lumping and bumping about hadn't done the optics much good.

These compound VC200L scopes aren't the easiest things to collimate, but fortunately there's a good guide here. A few tweaks with an Allen key on the primary mirror adjustors soon got the star images sharp again, and I plan to return to M57 and try to get a better resolved image.

Even so, the image above still shows the 15th magnitude barred spiral galaxy IC1296 to the northwest of M57 - most images you see don't go deep enough to evidence it, especially those taken with digital cameras.

My own earlier (August 2002) effort with a digital camera (afocal projection using the VC200L and a 25mm eyepiece) is shown below (click to enlarge).


This is an average of two 60 second exposures taken at ISO400 and processed in PSP. I haven't adjusted the colours at all, only the contrast and brightness. Whilst the digital camera is noticably less senstive than the SXV-H9 and shows fewer stars, the image itself is still quite satisfying.